Some people have car stereos that can do that in the audible range.
When I hear their stereos thumping at stoplights (mine and their windows rolled up) I like to think that they are slowly fatiguing all the spot welds holding their little tuner buzz bombs together, and one day their car will just fall apart.
The damage to their eardrums is the subject of a completely different thread.
I do wonder if anyone did something rash like installing 10^lots of watts in an old cold-war Skoda or some such and
actually burst their vehicle on first test!
Could the technology be useful though - perhaps clearing leaves from a lawn and stacking them up in a neat bonfire
pile!
The strangest one I've seen is this...
Acoustic method for levitation of small living animals
W. J. Xie, C. D. Cao, Y. J. Lü, Z. Y. Hong, and B. Wei
Citation: Applied Physics Letters 89, 214102 (2006); doi: 10.1063/1.2396893
View online: http://dx.doi.org/10.1063/1.2396893
I've had an interest in this topic in relation to aerosols for several years. Aerosols and particles on the order of 1 micron in size move to the velocity nodes (pressure anti-nodes). The theory of that is relatively simple and depends on linear Stokes drag forces.
Larger particles and objects are subject to an additional force that depend on nonlinear acoustics, where air molecules scatter off the object (rather than flowing around it), and this is called radiation pressure. This force moves the particle/object toward the velocity antinode. In the case of levitation, that is balanced against the force of gravity. The nonlinear effect only becomes significant in strong acoustic fields. They are pouring hundreds of watts into that field. I'm looking for a dB figure!
For aerosols, one of the effects in a high sound field is that particles collide and become larger aggregates. That has practical applications in filtering toxics. Also, there are a number of patents having to do with acoustic separation of particles, for concentration or analysis.
Their background publication is available as a pdf here.
They claim that the sound pressure at the focal point is up to 5200 Pa RMS at 40kHz. Atmospheric pressure is 101325 Pa, so that sound pressure is around 5% of atmospheric. In auditory terms, it is 168dB, compared to the threshold of hearing at 0dB, 0.00002 Pa, 1000Hz, or the threshold of pain at around 120dB.
erco
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When I hear their stereos thumping at stoplights (mine and their windows rolled up) I like to think that they are slowly fatiguing all the spot welds holding their little tuner buzz bombs together, and one day their car will just fall apart.
The damage to their eardrums is the subject of a completely different thread.
Whenever "her in doors" starts shouting I levitate instantly
actually burst their vehicle on first test!
Could the technology be useful though - perhaps clearing leaves from a lawn and stacking them up in a neat bonfire
pile!
Or preventing flies entering an open window?
The strangest one I've seen is this...
Acoustic method for levitation of small living animals
W. J. Xie, C. D. Cao, Y. J. Lü, Z. Y. Hong, and B. Wei
Citation: Applied Physics Letters 89, 214102 (2006); doi: 10.1063/1.2396893
View online: http://dx.doi.org/10.1063/1.2396893
I've had an interest in this topic in relation to aerosols for several years. Aerosols and particles on the order of 1 micron in size move to the velocity nodes (pressure anti-nodes). The theory of that is relatively simple and depends on linear Stokes drag forces.
Larger particles and objects are subject to an additional force that depend on nonlinear acoustics, where air molecules scatter off the object (rather than flowing around it), and this is called radiation pressure. This force moves the particle/object toward the velocity antinode. In the case of levitation, that is balanced against the force of gravity. The nonlinear effect only becomes significant in strong acoustic fields. They are pouring hundreds of watts into that field. I'm looking for a dB figure!
For aerosols, one of the effects in a high sound field is that particles collide and become larger aggregates. That has practical applications in filtering toxics. Also, there are a number of patents having to do with acoustic separation of particles, for concentration or analysis.
They claim that the sound pressure at the focal point is up to 5200 Pa RMS at 40kHz. Atmospheric pressure is 101325 Pa, so that sound pressure is around 5% of atmospheric. In auditory terms, it is 168dB, compared to the threshold of hearing at 0dB, 0.00002 Pa, 1000Hz, or the threshold of pain at around 120dB.